1. Field of the Invention
The present invention relates to a method for fabricating a nitride-based compound layer, a GaN substrate and a vertical nitride-based semiconductor light emitting device. More particularly, the present invention relates to a method for fabricating a nitride-based compound layer, a GaN substrate and a vertical nitride-based semiconductor light emitting device capable of recycling the expensive GaN substrate by forming a mask layer with a predetermined pattern and a buffer layer on the GaN substrate, laterally growing the nitride-based compound layer, and removing the mask layer and the buffer layer via wet-etching to separate the GaN substrate without impairment.
2. Description of the Related Art
In general, a nitride-based compound is a group III-V compound crystal such as GaN, InN, and AlN, which is widely used for a light emitting device generating light of a short wavelength (ultraviolet ray and green light), especially blue light. The nitride-based compound has been typically manufactured via a sapphire substrate or a SiC substrate due to absence of a commercially available substrate that satisfies lattice match conditions for crystal growth. But the sapphire substrate or SiC substrate has lattice mismatch with the nitride-based compound. This renders it very difficult to grow a high-quality nitride-based compound on the sapphire or SiC substrate.
Meanwhile, a substrate having lattice match with the nitride-based compound, such as a GaN substrate, has been fabricated. However, the GaN substrate is very expensive, and unrecyclable owing to grinding and abrasion that occur during lapping and polishing in a manufacturing process of the light emitting device.
FIG. 1 is a cross-sectional view partially illustrating a method for fabricating a nitride-based light emitting device using a GaN substrate according to the prior art. As shown in FIG. 1(a), in a conventional method, a light emitting structure 12 made of a nitride-based compound semiconductor is formed on a GaN substrate 11 with a predetermined thickness d. Then in order to easily separate a final structure obtained into individual devices, an underside of the GaN substrate is ground and abraded via lapping and polishing to reduce the thickness d′ of the GaN substrate 11 as shown in FIG. 1(b).
This conventional method for fabricating the nitride-based semiconductor light emitting device using the GaN substrate is disadvantageous in that the high-priced GaN substrate is unrecyclable due to grinding and abrasion caused by lapping and polishing.
Therefore, in the art, there has been a demand for a technology of recycling the high-priced GaN substrate to reduce production costs.